High-speed parallel printer

ABSTRACT

An on-the-fly printer having a continuously rotating drum including multiple side-by-side columns of characters, and having multiple spring-energized acceleration and print impact mechanisms associated with the respective character columns, the acceleration and impact mechanism being mechanically restored to, and latched in, energy-stored positions from which they can be selectively released each to drive a separate hammer against paper and/or paper forms inserted between the mechanism and the character drum, the release being accomplished by electronic control circuitry operative to determine when the angular position of the drum is correct and thereupon to print characters located in that row of the drum in one or more of the digit positions corresponding with the various columns of print, the electronic control circuitry subsequently enabling a restore mechanism to retract and latch all of the acceleration and impact mechanisms as soon as a row or line of digit positions has been printed, the printer automatically advancing paper tapes as well as manually inserted forms to the next print position during each operation of the restore mechanism.

United States Patent [19;

Murthy et al. 1 Apr. 3, 1973 [54] HIGH-SPEED PARALLEL PRINTER Primary Examiner-William B. Penn [75] Inventors: Nanjundiah Narasimha Murthy, A"mey Arthur w at West Redding; Joseph Steven Macura, Trumbull; William Gergely, Jr., [57] ABSTRACT Faiffield; Allen. Charles Berg An on-the-fly printer having a continuously rotating of Colmdrum including multiple side-by-side columns of [73 A i pimey Bowes A|pex, Inc" Danbury, characters, and having multiple spring-energized ac- 7 C celeration and print impact mechanisms associated [22] Filed: Dec. 13, 1971. with the respective character columns, the acceleration and impact mechanism being mechanically [21] Appl.N0.: 207,114 restored to, and latched in, energy-stored positions xfrom which they can be selectively released each to [52] U.S. Cl. ...101/93 C, 19;!!133 R drive a separate hammer against paper and/or paper {2 2 forms inserted between the mechanism and the i 19 1/1 character drum, the release being accomplished by p I eltelctrczaic conltrol cirtcuitryf (tJIEJCI'ZtIYE to detertming w en e an uar 051 ion 0 e rum IS correc an ,[56] Reterences Cltgd thereupon to prini characters located in that row of UNITED ATE A E the drum in one or more of the digit positions corresponding with the various columns of print, the eleczl i tronic control circuitry subsequently enabling a 3 385 211 5/1968 shefi 'riliiiiliiIIIIIIIII :::101/93 0 mechanism to retract and latch the 3:420:l66 l/l969 Ellis et al. ..l0l/93 c 16mm and impact mechanisms as 80011 as a row of 3 490 3 1970 Benson et L 101 93 C line of digit positions has been printed, the printer au- 3,55 6,002 1/1971 Braggl ..101/93 C tomatically advancing paper tapes as well as manually 3,524,528 8/1970 Peyton..... l97/l33 R inserted forms to the next print position during each 1971 g i g C operation of the restore mechanism. oey

33 Claims, 11 Drawing-Figures PATENTEDAPR 3 I973 sum 1 OF 3 WILLIAM GERGELY,JR. a ALLEN CHARLE PATENTED APR 3 I875 SHEETEUF8 INVENTORS NANJUNDIAH NARASIMHA MURTHY JOSEPH STEVEN MACURA WILLIAM GERGELY, JR. 8

ALLEN CHARLES BERG WfM ATTORNEYS PAIENIED P 3 SHEET :1 e n O Q m N It m .N

as N

N N Q r 2 a N N v INVENTORS NANJUNDIAH NARASIMHA MURTHY JOSEPH STEVEN MACURA WILLIAM GERGELY, JR. 8 ALLEN CHARLES BERG QIORNEYS PATENTEDAPR3 I975 3,724,366

SHEET l 0F 8 INVENTORS NANJUNDIAH N ARASIMHA MURTHY JOS H STEVEN MACURA 0 wu. AM GERGELY JR.8|

ALLEN c HARLES BERG ATTORNEYS PATENTEBAPR 3 I975 SHEET 5 BF 8 INVENTORS NANJUNDIAH NARASIMHA MURTHY JOSEPH STEVEN MACURA WILLIAM GERGELY JR. 3 ALLEN CHARLES BERG BMW ATTORNEYS PATENTEDAPRIS ms 3.724.366

SHEET 6 [1F 8 INVENTORS NANJUNDIAH NARASIMHA MURTHY JOSEPH STEVEN MACURA WILLIAM GERGELY, JR. 8

ALLEN CHARLES BERG PATENTEDAPRB I975 SHEET 7 OF 8 INVENTORS NANJ UN DIAH N ARASIMHA MURTHY JOS E PH STEV EN M ACURA WILLIAM GERGELY JR8| ALLEN CHARLES BRG ATTORNEYS HIGH-SPEED PARALLEL PRINTER This invention relates to high speed on-the-fly parallel printers of the type generally used in conjunction with electronic data processing systems, such as an electronic register or calculator system, and more particularly relates to a printer especially useful in connection with point-of-sales cash register systems, for instance of the type used in department stores, etc.

The prior art includes many printers designed to be attached to systems of one type of another including on-the-fly printers in which a multiple-column character drum continuously rotates, and printing is accomplished by selectively impacting paper against the characters in the various moving columns until a whole row of digit positions has been printed upon the paper, and then advancing the paper. It is to this general type of printer that present improvements are directed.

It is an important object of the invention to provide a printer and associated electronics in which a whole row of digit positions can be printed in no more than one complete drum revolution, and in which the acceleration and character drum impacting mechanisms are almost immediately restored to their energy-stored positions and the paper is concurrently advanced so that the printer system is ready to begin a new print cycle at once without wasting time waiting for the drum to return to some arbitrarily selected start position, which return would require at least a part of one revolution.

It is another major object of the invention to provide a printer in which mechanical functions and electronic functions are combined in an optimum blend in which print hammers are accelerated by the release of spring means to impact paper against a character drum being continuously rotated by a motor. This same motor also supplies the relatively large amount of torque necessary to retract the acceleration and impact mechanisms to restore energy in their springs after each print cycle, and to also advance the paper. These functions and others are controlled by electronic control means which not only initiate the restore cycle of the acceleration and impact mechanisms, but also sense the angular position of the drum and release the mechanisms to strike the drum whenever appropriate characters in the various adjacent identical columns of the drum reach print position during a print cycle. The mechanical system cooperates with means for feeding back to the electronic control circuitry various information, such as cyclically receiving events including the present position of the character drum, and also including indications of other events such as the intervention of the operator to manually initiate feed of the paper or to insert a paper sales form into the slot provided for that purpose, etc.

When the printer is idle no power is required to maintain the print hammer means in energy-stored condition, i.e., ready, to print the next row of characters when actuatedby the electronic control means.

It is a further important object of the invention to provide a printer which is highly versatile and can be readily adapted for use with different types of computer or register systems. Mechanically, the printer comprises a main frame carrying a drive motor, and having paper feed means, a continuously rotating character drum, inking means therefor, a print energy and restore assembly, and the control mechanisms for these components. In the illustrative example included in this specification the print energy and restore mechanism is a removable sub-assembly which is easily installed opposite the character drum on the main frame. Thus sub-assembly includes opposite each character drum column a print hammer acceleration and impact mechanism including a hammer, a bellcrank having one leg disposed to accelerate the hammer and having its other leg urged by an impactpower spring, and print mechanism latching and release means. The sub-assembly also includes means for restoring all of the acceleration and impact mechanisms to latched position. The sub-assembly is supported on the main frame opposite the drum by a few quick-detach fasteners, and is therefor readily separable from the main chassis for service. This construction, being modular, also permits flexible choice of whatever print mechanism is needed for printing various different types of information. In one presentlymanufactured embodiment the printer includes a print drum having 22 columns of characters, all of the columns being identical and transversely mutually aligned so that the characters appearing in each of 40 rows across the face of the drum are all similar. In this embodiment of the invention the 40 characters include the alphabet, numerals 0 through 9, and certain other punctuation and special purpose marks. This drum is inked by a separate ink saturated porous roller which is retracted away from the drum whenever the printer is not in service, but is automatically moved into contact with the drum when the printer is operative. Thus, the paper nearest the drum is impacted directly against its characters and is therefore printed by wet ink, but other papers in the print position are printed by the insertion of carbon, or by the use of a self-imaging type of paper. Theprint drum is housed within a cantilever portion of the main printer frame, and in fact comprises a part of the main frame which extends to one side thereof, and there are paper guiding plate means which extend past one surface of the cantilever assembly and have openings therein through which the paper is impacted against the drum by the mechanism in the print energy and restore sub-assembly, which is located adjacent to the paper guiding plates opposite the drum. In the above-mentioned manufactured embodiment of the invention a roll of dual paper tape is carried on a spindle within the printer and the several paper tapes fed from the roll and pass between the paper guiding plates and emerge therebeyond. One of the tapes comes out of the printer past a tear-off blade so that it can be separated and handed to the customer as a receipt, and the other paper tape comprises a chronological tape which is stored upon a driven take-up roll within the printer and forms a record of the transactions. Between another pair of the paper guiding plates, an operator of the system can insert sets of paper forms or cards, for example, comprising cash sales forms, lay-away-plan forms or credit sales forms which are then printed by the same print mechanism simultaneously with the dual paper tape, so that all printed records must necessarily be identicalsince they are made in the same printer. Special care is taken to positively drive every one of the feed rollers which advance the tape and the inserted paper forms so that the papers do not slip with respect to each other as they are advanced. When inserting a paper form by hand, the operator will manually retract the grip of the feed rolls and insert the form into a suitable papersreceiving slot defined by two of the paper guiding plates. Two sensors are provided to detect when the form is fully inserted and the feed rolls are again engaging the paper, these sensors then delivering signals to the electronic control system to permit resumption of printing.

Still another major object of the present invention is to provide an improved print energy and restore mechanism comprising the parts mentioned above as being a separable sub-assembly, it being desirable but not necessary that the sub-assembly be separable from the main frame. This sub-assembly comprises a fulcrum block machined to provide slots in which a plurality of bellcranks are pivotally mounted side-by-side to correspond with the desired number of print digits, these bellcranks respectively comprising parts of the acceleration and impact mechanisms held between opposed side plates to form an integrated unit. Because of its modular construction, the number of such mechanisms can easily be varied to match the number of columns provided by a particular character drum. The print energy and restore sub-assembly includes a comb-like hammer supporting and guiding plate, having a number of slots therethrough which are spaced apart by the same spacing as the character columns on the drum, and these slots support the impact members which are referred to herein as hammers, and which are not rigidly connected to any other portion of the acceleration and impact mechanism. These hammers all comprise carefully-selected individual but identical masses which are respectively accelerated toward the paper to impact it against the print drum when the spring energy of the hammer acceleration mechanism is released. These hammer acceleration mechanisms are supported by shafts extending through the aforementioned fulcrum block and include said bellcranks which have first legs which underlie the hammers to strike them toward the paper and have second legs which are attached to individual power springs supported by the fulcrum block. A latch mechanism is also supported on the fulcrum block for each bellcrank, and this latch mechanism latches the bellcrank in such a position as to store energy in the associated spring with the hammer retracted from the paper. The sub-assembly also includes decks of latch-release solenoids which are selectively operated by the electronic control circuitry each to release an associated latch and permit the first leg of the released bellcrank to accelerate the associated hammer toward the paper to impact the latter against the rotating character drum. The novel restore mechanism comprises restore bails which extend across the bellcranks and are connected to cam followers which ride upon cams located at each of the side plates of the sub-assembly, assembly, the cams being carried upon a common restore shaft. When rotated, these cams pull the bails in a direction to relatch the bellcranks in energy-restored position. The electronic control includes means for actuating a clutch to couple the restore shaft to the main motor drive after each print cycle of the mechanism. The paper is advanced during the rotation of the cams when the restore shaft is engaged by the clutch.

It is a further major object of the invention to provide an improved print energy system in which the accelerating bellcranks are separate from the impact hammer means for the purpose of divorcing the mass of the hammer which strikes the paper to impact it against the drum from the mass of the bellcrank which is spring urged from latched position to accelerate the hammer mass, the bellcrank portion of the mechanism being inherently of much greater mass than the hammer. In view of the fact that the character drum rotates rapidly, it is very important that the dwell time of the impacting hammer mass be kept to a minimum so that the rotating characters are not smeared upon the paper. In general, the hammer must be accelerated at a high rate but must have only the minimum mass required to accomplish printing of the inserted multiple card and paper layers, whereby its energy is well dissipated as a result of the first impact so that when it rebounds therefrom it will lack sufficient energy to impact the paper a second time. If the bellcranks were made integral with the hammer masses, the latter could not be selected independently of the former masses to provide optimum printing while at the same time minimizing secondprint rebound.

Another important object of the invention is to provide a lightweight wire spring acting upon each hammer, the spring contacting a stationary part of the print energy sub-assembly so that when the hammer retreats back again after impacting the paper, its spring will help retain the hammer in its rest position by helping dissipate any kinetic energy which might tend to make the hammer bounce toward the paper a second time. The wire spring on each hammer is provided with loops on each side of the hammer to give the spring greater flexure.

Still a further important object of the invention is to provide means for preventing undesired printing of the paper in an adjacent column when a character next to it is printed by a hammer impacting the paper. Such an isolation means is important especially where the character drum is wet-inked since accidental printing will result even from very light contact with the inked drum. In order to accomplish adjacent-column character isolation, the present system teaches the use of barriers extending between the adjacent print columns of the character roll. These barriers may comprise a grid of wires resembling an egg slicer and extending across the apertures in the paper guide plate nearest the print drum, such wires passing tangentially between the columns. By having the wires extend radially outwardly from the character drum very slightly further than the print surfaces of the characters, when a hammer strikes the paper against a character in one column, the paper will be held away from the characters in adjacent columns by the wires. In a preferred,

embodiment of the invention rigid blades are used instead of wires, the blades being slightly higher than the characters as measured radially from the axis of rotation of the drum.

Another object of the invention is to provide a print hammer acceleration and impact mechanism having features of adjustability, including means for adjusting the energy stored in the power springs which respectively energize the hammer acceleration means to drive the hammers toward the paper. Another feature includes adjustability in the individual solenoid latch tripping means such that the solenoids all release the hammer accelerating means at the same relative times in response to similar electronic release signals.

Other objects and advantages of the invention will become apparent during the following discussion of the drawings, wherein:

FIG. 1 is a perspective view of an assembled printer according to the present invention with the cover plates removed so as to make the paper handling and printing mechanisms visible;

FIG. 2 is a perspective view of the same printer, taken from a different angle and showing the embodiment partly disassembled;

FIG. 3 is a perspective view of the mechanical drive side of the printer unit showing the means by which it is powered;

FIG. 4 is an enlarged partial view showing one side plate of the print energy and restore sub-assembly, and in particular showing part of the restore mechanism carried thereby;

FIG. 5 is a similar view of the print energy sub-assembly with the side plates removed to make the print hammer acceleration and impact mechanism visible;

FIG. 6 is another view of the sub-assembly, similar to that shown in FIG. 5, but showing one of the hammer acceleration means released to drive the hammer to impact the paper against the character drum;

FIG. 7 is a perspective view showing several acceleration bellcranks and hammer means mutually oriented in intermeshing relationship;

FIG. 8 is a fragmentary section view taken along line 8-8 of FIG. 6 and showing means for isolating adjacent character columns so as to prevent one column from printing when the adjacent column is impacted;

FIG. 9 is an enlarged detail view of means for driving paper-advancing rollers;

FIG. 10 is a detail view showing three plates for guiding the paper between the character drum and the print energy and restore sub-assembly; and

FIG. 11 is a block diagram of the printers electronic control circuitry.

Referring now to the drawings and especially to FIGS. 1, 2, and 3, the illustrative embodiment of the printer comprises a main frame 10 which includes a main vertical divider wall 11 dividing the machine into a left portion including the print mechanism which is seen in FIGS. 1 and 2, and a right portion including the belt drives and associated mechanisms which are shown best in FIG. 3. The main frame includes suitable chassis mountings such as the foot 12, and near the front of the machine (upper right portion of FIG. 1) the frame has horizontally extending boss portions 13, 14 and 15 as well as a front plate portion 16, all extending toward the viewer in FIG. 1. These support a side plate 29 and together form a cantilever assembly 30 which, as can be seen in FIG. 2, stands horizontally outwardly from the frame divider wall 11 in cantilever fashion. There is also another horizontally extending portion 17 near the center top of the frame which supports certain paper guiding plates as will be discussed hereinafter, the boss portion 17 being most clearly visible in FIG. 2.

The portion of the assembly bounded by the vertical wall 11 and the bosses 13, 14, 15 and the front plate 16, which were referred to above as the cantilever assembly, houses a print character drum 20 and an inking roll 22 which is pivotally supported for movement toward and away from the character drum 20. The end of the character drum 20 which is visible in FIGS. 1 and 2 is supported in a bearing 24 through which the shaft 21 of the character drum extends. Furthermore, the inking roll 22 is supported on a shaft 23 which is journaled at its near end in an arm 25 fixed to a rocker shaft 26 whose ends are visible in FIGS. 1, 2 and 3, the near end of the rocker shaft 26 being supported in a bearing plate 27, and the far end of the shaft being supported in a bearing 28 for the purpose hereinafter discussed. The bearings 24 and 27 are mounted on the cantilever side plate 29, and the rotation of the character drum 20 as well as the rocking of the inking roll 22 toward and away from the drum is controlled by mechanisms mounted on that side of the vertical divider wall 11 which is shown in FIG. 3.

The present embodiment of the printer includes three guiding plates 31, 32 and 33. The plates 32 and 33 are separated by spacer means 33d and guide the paper tapes between them, and inserted paper forms are guided between the plate 32 and the plate 31 which comprises a part of the cantilever sub-assembly 30. These three plates are also seen in FIG. 10. In FIG. 2 the print-energy sub-assembly as well as the two lower plates 32 and 33 have been removed, but they are visible in FIG. 1 and occupy the space beneath the cantilever assembly 30 and the print energy assembly which is generally referred to in FIG. 1 by the reference numeral 100. By inspection of paper guide plate 31 it can be seen that the plate has two apertures in it including a slot 31a which opens to reveal the print character drum 20 and a slot 31b through which paper feed rollers such as the rollers in FIG. 2 can grip the paper which passes upwardly between the guide plates. A slot 34 is provided to receive paper forms when manually inserted, this slot lying between the guide plate 31 and the center guide plate 32. The mouth of the slot is widened by having the upper guide plates 31 flare as at 31c away from the central guide plate 32 to provide an entrance through which an operator can insert sales forms in the manner discussed below. The upper end of the slot 34 comprises the paper exit end, and the guide plate 31 is also flared at that end as shown at 31d. The central paper guide plate 32 terminates at its upper end just below a tear blade 37 at the exit end of the slot, and the lowermost guide plate 33 joins an exit plate 36 which extends beyond the tear blade 37. The central paper guide plate 32 has an opening 32a through it, and the bottom guide plate 33 has openings 33a and 33b through it, and when the plates are assembled all these openings register with each other opposite the character drum 20 and the paper feed rollers 40.

As can be seen in FIG. 1, a paper supply roll feeds a dual paper tape 51 and 52 across the bottom of the machine and around a curved end 330 of the guide plate 33, both of the paper tapes 51 and 52 extending back up through the slot between the cantilever assembly 30 and the print energy mechanism 100, and more particularly extending between the central plate 32 and the lower plate 33. The dual tapes 51 and 52 are then separated from each other by the exit plate 36, the tape 52 extending above the plate 36 and beneath the tear off blade 37. The tape 51 passes below the exit plate 36 and over the top of a plate 56 which is carried on the boss 17, the tape 51 finally being rolled up upon a tape reel 53 which is supported in a bearing (not shown) located in the vertical divider wall 11. The reel 53 is supported on a shaft 54 which is driven by a friction slip clutch 55 driven by a belt which will be discussed hereinafter. The shaft 54 and the clutch 55 are visible to the right in FIG. 3.

FIGS. 1 and 4 through 7 show the print energy and restore sub-assembly 100 and the various components thereof. This sub-assembly comprises two side plates such as the plate 101 which can be seen best in FIGS. 1 and 4, and these side plates are separated by a distance substantially equal to the width of the cantilever assembly 30 as measured perpendicular to the main vertical divider wall 11. The two end plates are bolted to a fulcrum block 105 located between them and supporting a plurality of print hammer acceleration and impact mechanisms in adjacent modular relationship, see FIG. 5. They also support four solenoid decks in the present embodiment, the solenoid decks comprising two upper decks 137 and two lower decks 138 which are more clearly visible in FIGS. 5 and 6. All of these parts are attached to the side plates 101 by brackets l44'and 145. The power springs and bellcranks which are part of the aforementioned acceleration and impact mechanisms, and which accelerate the hammers themselves, are supported on the slotted fulcrum block 105 in a position parallel to the side plates 101. The fulcrum block 105 is best seen in FIGS. 5 and 6 and supports on each side of it one-half of the acceleration bellcranks. The block 105 is then supported upon bolts, such as the bolts 104, which pass through the holes 106 on each side of the fulcrum block. The fulcrum block 105 is recessed'as shown at 107 and carries two pivots 110 which pivotally support the bellcranks 111 which are typical of the hammer acceleration assemblies, each bellcrank serving to accelerate its associated hammer 120. The bellcranks each have a first leg 112 which extends into the recessed portion 107 of the fulcrum block so that the ends of the legs 112 intermesh with each-other without touching as can best be seen in FIG. 7. Preferably the bellcranks are pivoted on two fulcrum shafts 110 in alternating mutual relationship extending from opposite sides of the fulcrum block 105 so that they are separated or spaced from each other by machined slotsin the fulcrum block itself. The other leg 113 of each bellcrank has an eye at its upper end which is connected to a power spring 115 from which energy is derived to accomplish the actual printing impact. The outer end of each ofthe springs 115 is supported on-a bendable tab 1 16 which is in turn bolted to a small, flange on the fulcrum block 105. Thus, the spring 115 urges the bellcrank 111 to rotate around its pivot 110 in such a way as to urge the outer end of the first leg 112 upwardly. The outer end of each leg 112 terminates in an a'rcuate foot 112a which lies against the lower end of an associated hammer member 120. The mutual orientation of the hammer and its bellcrank is most clearly shown in FIG. 7. There is a hammer associated with each bellcrank and located opposite each column of print on the character drum 20. The hammers are all supported in a comb guide- 122 which is held at its ends between the side plates 101, the guides 122 having locating pins on their ends which sit in the holes 1 17 of the side plate 101, FIG. 4. The comb members 122 provide vertical slots which are separate from each other and each of which supports a hammer so that it is free to reciprocate up and down as illustrated in FIGS. 5 and 6. It is the hammers 120, one for each digital position, which actually accomplish the printing impact when they are accelerated upwardly by sudden release of the bellcranks 111 to permit their. springs 115 to rotate and raise their outer ends 112a rapidly upwardly.

The bellcranks are normally held down in the energy-restored position shown in FIGS. 5 and7 by latch arms and 131, these arms performing similar functions but the arms 131 being longer than the arms 130. The arms 130 and 131 are respectively pivotally connected to the fulcrum block 105 by upper and lower pivots 132 and 133, these pivots being best illustrated in FIG. 7. The upper pivots 132 support the shorter latch arms 130 and the lower pivots 133 support the longer latch arms 131, these arms being respectively supported by the fulcrum block 105 beneath the corresponding leg 112 of the associated bellcrank. Still referring to FIG. 7 it willbe noted that the outer end of the leg 112 of each bellcrank 111 terminates in a latching tip 114 which is engaged by the hooked end 134 of a latch arm such asthe arm 130 in FIG..7. Thus, the bellcrank is latched in down position ,by its latch arm which is normally pivotally urged toward latching position by a suitable spring 1 l On the other hand, when a character is to be printed by a particular hammer and acceleration means, its associated solenoid 137 or 138 as the case may be is energized by the electronic system to be discussed hereinafter to drive its plunger downwardly as shown in FIGS. 5 and 6 in order to presstliei latch arm toward a released position by stretching thespring 119. The armature of the solenoid is in each case connected to a forked push rod such as therods 139 or 136, these rods thereby releasing the catch which holds the bellcrank in energy-restored position. The normal retracted position of the push rod and the solenoid armature is controlled by a screw adjustment 140 in the-case of theupper solenoid deck and 141 in the case of the lower solenoid deck, these screws setting the length of the solenoid stroke when the associated catch 'arm is releasing the bellcrank from its energy-restored position, which is the position shown in -FIG. 5 for the bellcranks appearing on both sides of the block 105. The solenoids 137 and 138 are respectively supported on frame members 142 and 143 whose outerends 144 and 145 can be seen in FIG. 1 and in FIG. 4. These outer ends are attached to the side plates 101 at the tabs 101a shown in FIG. 4.

FIGS. 1, 4, 5 and 6 also show the mechanism by which all of, the bellcranks are from time to time cocked into the energy-restoredpositions. For this purpose, there are two energy-restore bailmembers 154 and 155 which can be seen best in FIG. 4. Each of the bail members comprises two crank arms, one at each end, similar to the arm on the right side of FIG. 4 or the arm 151 on its left side. The restore bail member has each of its arms 150 or 151 pivoted upon a pivot 152 or 153 by which it is supported at opposite sides on the plates 101. The two restore means are located above their respective bellcrank arms 112 and contact them whenthe bails are moved downwardly. The bail 154 extends between the two arms 150 and integrally joins them, and the bail 155 extends between the two arms 151. The position of these bails 154 and 155 with respect to the first legs 112 of the bellcranks can be clearly seen in FIG. in which the bellcranks 111 are in cocked position, and in FIG. 6 in which the left bellcrank has been released but the right bellcrank is still in cocked position. It will be noted that when the crank is released position the top of its leg 112 as shown to the left in FIG. 6 lies against and is stopped by a stationary stop 102, and that in this released position of the leg 112 the hammer 120 is not long enough to contact the paper at its upper end and still lie on the foot 1 12a at its lower end, whereby the printing is accomplishedby the inertia of the hammers mass. As shown in FIG. 6 the hammer is just impacting against the paper.

Each restore means also includes an extension labelled 156 and 157 in FIG. 4 and each extension is joined to a restore link 160 or 161 as can best be seen in FIGS. 1 and 4. Thus, when the restore links 160 and 161 are pulled downwardly, the bails 154 and 155 contact the legs 112 of the bellcranks and pull them downwardly into latched position, all of them being pulled simultaneously. The restore links are bowed outwardly at their lower ends and are joined together by a shaft 164 which is carried upon a radius arm 165 connected at the pivot 166 to the side plate 101, this assembly being shown in FIG. 4 and also repeated at the other side plate (not shown). The radius arm 165 has an upward extension 167 which is biased by a spring 168 to urge the shaft 164 vertically upwardly. The shaft 164 also carries at each end a rotatable cam follower 169 which rotates against the surface of a cam 170 at each end of the cam shaft 171 whenever the cam is rotated. The cam 170 is supported upon the shaft 171 to which it is keyed, the shaft 171 extending through the main frame vertical divider wall 1 1. The shaft 171 is periodically rotated by the drive means shown in FIG. 3, as will be hereinafter explained in greater detail, and each time the shaft 171 and the cam 170 are rotated half a turn, the cam followers on the shaft 164 are moved downwardly so that they pull the links 160 and 161 down with them, thereby driving the bails 154 and 155 downwardly to latch the tips 114 of all of the bellcranks 1 11 into the lowered position as shown in FIG. 5, and as shown with respect to the bellcrank located on the right in FIG. 6.

On the other hand, when a solenoid 137 or 138 is energized, the latch arm 130 or 131 is pivoted so as to release the tip 114 of the associated bellcrank and allow the spring to accelerate the foot 112a upwardly and thereby drive the hammer 120 to impact the paper 51 and 52 against the type in the associated column of the character drum as shown in FIG. 6. The spring 123 which is carried by each hammer 120 bears against the lowermost guide plate 33 of the paper guides and controls the rebound of the hammer so that, upon its return after impact, it will not again bounce into a second contact with the paper. The loops 124 in the spring 123 are designed to provide them with increased flexure. I

FIG. 6 and 8 show isolation means for preventing a character in one row from printing on the paper when the character in the adjacent row is printed by a hammer 120 impacting the paper against the inked character drum 20. This can be seen best in FIG. 8

which shows barriers 127 extending substantially tangentially across the bottom of the character drum 20 and located between the characters in adjacent rows, such rows being labelled 20a in FIG. 8. These barriers 127 as shown in FIGS. 6 and 8 comprise individual blades which are all joined together at both ends by integral supporting webs 126. The webs 126 are secured by screws 128 to stationary frame members 18 and 19 which are mounted in fixed relationship with respect to the character drum 20 in suitable manner (not shown). Thus, the individual barrier blades 127 are supported just outside of the radial location of the character faces in the columns of the character drum 20. Note for example in FIG. 8 that the paper 52 is in contact with each of the barrier blades 127 and that these blades are spaced in such a way as to hold the paper 52 away from the drum except where it is actually impacted against the drum by a hammer 120. FIG. 8 also shows the manner in which the springs 123 are secured in slots in the sides of the hammers 120, and then soldered in place.

An alternative form of isolation means for suppressing undesirable printing in columns located adjacent to columns being impacted can comprise a number of fine spring wires instead of the blades 127, these spring wires being secured at their ends in holes in supporting blocks which are secured to the frame members 18 and 19 by the screws 128 at their outer ends. This modification provides a similar result, but is not illustrated in the drawings.

DRIVE MECHANISM The drive which performs the necessary mechanical functions described hereinbefore is illustrated for the most part in FIG. 3 of the drawings, this drive mechanism comprising an electric motor which drives a series of belts and pulleys through which it performs most of the mechanical functions of a type requiring a considerable amount'of power, for instance, the continuous rotation of the character drum, the restoring to cocked portions of the various print hammer mechanism to thereby restore the energy into the springs which furnish the printing impact, and the timely advancing of the paper tape including its take-up means. The other mechanical motions are generally provided by individual solenoid means, some of which have already been mentioned above.

Referring more particularly to FIG. 3 a motor M, which is mounted on a plate (not shown) attached to chassis holes H, drives a pulley at its lower end as shown in FIG. 3, and this pulley in turn drives a main drive belt 181. The belt 181 passes around a pulley 182 which drives the character drum shaft 21 and is located on the other side of the wall from the character drum 20. The main drive belt 181 in addition passes around the normally freely-rotating lower pulley of a clutch assembly 183 which is normally disengaged, and then the belt returns to the pulley 180 on the motor shaft. Since the motor rotates continuously whenever the system is turned on, the shaft 21 is also continuously rotated so that the character drum 20 is always in motion and one side of the clutch 183 is also continuously rotated, The upper pulley 184 of the clutch 183 normally stands still. This latter pulley 184, when engaged derives power from the lower clutch pulley and then drives a restore lll mechanism belt 185 whose function will be further discussed hereinafter.

The pulley 182 which drives the character drum shaft 21 has a code disc 186 screwed to it so that as viewed in FIG. 3 the disc 186 overlies the pulley 182. The disc has a series of small index signal holes 187 around its outer periphery and in addition has one reset signal hole 188 located radially inwardly opposite one of the outer indexing holes 187. This disc-and-hole structure is of a type known in the prior art and used for encoding the position of the character drum. Each of the index holes 187 in the outer annular series is aligned with a different row of characters across the face of the character drum 20, but the double hole pattern including one index hole and the reset hole 188 is located opposite an arbitrarily-selected first character row of the drum. Light sources (not shown) are located behind the code disc 186, and provide two pinpoints of light, one opposite the photoelectric cell 191 and the other opposite the photoelectric cell 192. Thus, as the disc 186 rotates the index signal cell 191 receives a pulse of light each time the character drum aligns a new row of characters with the print hammers 120 through the window 31a as seen in FIG. 2. Moreover, when the thus-aligned row comprises the first row of characters, the reset signal photoelectric cell 192 also delivers a pulse. These photoelectric cells are both connected to an electronic circuit board 193 carrying components of the control circuitry which encodes the position of the drum using the pulses from these photoelectric cells and sends its output on a cable 194 as will be described hereinafter to other components of the electronic control system. The photoelectric cells 191 and 192 are supported upon a bracket 195 which is supported at its right end in a hinged arrangement including a stationary bracket 196 having a pivot pin extending through it whose ends have been labelled 197 in FIG. 3. Thus, the bracket 195 can be pivoted around the pin 197 to tip it up, at the same time disengaging its left end from the shaft 21, exposing the photoelectric system for service, and also making it possible to remove the code disc 186.

Each time a row of print has been entered on a business form inserted in the slot 34, and/or on the paper tapes 51 and 52, it becomes necessary to advance the paper to the next line-of-print position and to restore the potential spring energy to the print energy mechanism springs 115 in preparation for printing the next row of characters. These functions are accomplished in response to appropriate commands from the electronic control system. When the electronic control system has determined that a row of characters has been printed, the control system delivers a pulse which actuates the solenoid 201 to pull the left end of arm 202 downwardly, as viewed in FIG. 3, which therefore pushes the right end of arm 202 upwardly and disengages the pawl 203 from one of the notches around the outer periphery of the collar 204. Normally, the right end of the arm 202 engages the pawl 203 in one of the notches on the collar 204 and stops it from rotating. The clutch itself will not be described in detail because it is of conventional design, being of the type wherein a wrap-around coil spring located inside the collar 204 is held loosely about two drums respectively attached to the pulleys within the clutch whenever the collar 204 is engaged by the pawl 203. However, if the collar is freed to rotate, the spring wraps up on the drums and causes the lower pulley of the clutch 183 to drive the upper pulley 184 until the pawl 203 drops back again into the next notch and again causes the spring to unwrap and release the clutch. The clutch is designed such that each time the pawl is released from one of the notches of the collar 204 and let fall back into the next one, the upper pulley 184 is driven far enough to drive the pulley 206 on the shaft 171 through degrees through the belt 185. There are of course many other types of intermittent clutches that could be used in place of the spring clutch 183 as described hereinabove.

The pulley 206 is keyed to the shaft 171 of the restore mechanism in the print assembly as was described above in connection with FIG. 4. The drive causes the shaft 171 to rotate, and such rotation also causes an adjacently attached pulley to rotate and to drive the paper advancing belt 207. The rotation of the shaft 171 also drives the pulley 208 and thereby drives the belt 209 which in turn drives the pulley 55 and the shaft 54 for the purpose of advancing the paper take-up reel 53. The take-up reel is thus intermittently advanced whenever the restore mechanism of the printer is operated, and it will be recalled that the pulley 55 in-.

cludes a friction slip clutch so that the paper take-up reel 53 is only urged to rotate sufficiently to cause the slack to be taken out of the tape 51. v

The belt 207 can also be seen in FIG. 9 of the drawings which is a detail view of the mechanism by which the paper advancing rolls 40 are caused to rotate for the purpose of advancing the paper to the next character printing row. This mechanism includes a bearing bracket 211 which has a pulley 212 journaled thereon as is seen in both FIGS. 3 and 9, and this pulley drives a cam 210 which can be seen in dotted lines at the bottom of FIG. 9. Recalling that the belt 207 is driven only'when the restore mechanism is being intermittently operated, the cam 210 performs only one half of a revolution for each restore cycle of the system. In FIG. 9 each time the belt 207 is driven to rotate the cam 210 through one half a revolution, the cam follower wheel 213 is pushed upwardly as shown in FIG. 9 or upwardly and rightwardly as shown in FIG. 3. The cam follower wheel 213 is journaled in a bracket 214 which has an upper extension 215 visible in both FIG. 3 and FIG. 9. As can be seen in FIG. 9 the bracket 214 and extension 215 is supported on three pins labeled 216 and 217, the two pins 216 passing through slots in the lower end of the bracket and the pin 217 passing through a slot in the elongated neck 215 of the bracket. A spring 218 located at the upper end of the extension 215 as shown in FIG. 9 is stretched between the pin 217 and a turned-up tab 219 at the top of the bracket, the

spring tension urging the cam follower wheel 213 downwardly into contact with the cam 210 at all times. The paper-advance rollers 40 and 40a are respectively carried by two shafts, one of the shafts passes through the cantilever assembly 30, carries the rollers 40, and is labelled 221 in FIG. 2 and FIG. 9. There is also another pair of rollers 40a carried in the print energy and restore sub-assembly and supported on the shaft 222 as can be seen in FIGS. 1 and 9. The rollers 40a and 40 normally pinch the paper between them for the-purpose of feeding it through. The ends of the shaft 221 and 222 respectively carry ratchet wheels 225 and 226 which are engaged periodically by the pawls 227 and 228. This occurs when the cam follower wheel 213 is actuated upwardly by the cam 210 as viewed in FIG. 9. The pawls are respectively pressed toward the ratchet wheels by springs 229 and 230 so as to be sure that they will engage them. The pawl 227 is supported below the slide member 214 whereas the pawl 228 is supported on top of the slide member so that the two do not interfere with each other. The spacings between adjacent rows of characters as printed by the machine are maintained constant by providing a triangular star wheel 231 which is engaged by a detent 232 supported on an arm 233 which is pivotally mounted at its upper end and is spring urged at its lower end by a spring 234. By this means when the pawls 227 and 228 are retracted from the ratchet wheels 225 and 226 the triangular star wheel 231 will be precisely indexed by the detent 232. Some of the parts described in detail in FIG. 9 are also visible in FIG. 3.

The solenoid 201 is energized for only a brief instant so that it is released before the end of a quarter of a revolution of the clutch collar 204 whereupon the pawl 203 engages the next notch, and by this time the paper has been advanced and print energy has been restored to the hammer accelerating mechanisms by cocking the bell cranks 112 to retension the springs 115 in the print energy and restore sub-assembly. The releasing of the solenoid 201 allows the arm 202 to re-engage the pawl 203 in the next notch in the collar 204, thereby loosen ing the wrap-up spring, mentioned above as being located within the collar 204, to release the clutch and free the pulley 184 to idle on the shaft. As a result the belts 185, 207 and 209 are no longer driven, and the restore and paper-advance portion of the mechanism then remain motionless until the next time a row of characters has been printed and these mechanisms are again needed.

Near the bottom of FIG. 3 there is a solenoid actuator 237 which operates to pull the shaft 23 and the porous inking roller 22, FIGS. 1 and 2, into contact with the character drum 20. The inking roller 22 is carried on the shaft 23 whose end can be seen as fixed in the arm 238 in FIG. 3. This arm rocks about the shaft 26 and when the power is turned off holds the porous inking roll 22 out of contact with the character drum 20. In the out-of-contact position the arm 238 rests against the stop 239 which is part of the bracket 240 supporting the solenoid 237. This solenoid is energized whenever the printer power is turned on, whether it is printing or not and therefore the armature 241 pulls in toward the solenoid 237 and biases the shaft 23 toward the character drum 20 so as to make the roller 22 continuously ink it. i

The shaft 221 which supports the feed rollers 40 is supported in two places by a pair of arms, which are shown in dotted lines in FIG. 1 and in FIG. 9. These arms are respectively labelled 243 and 244. The arms 243 and 244 are pivotally connected to the frame between their respective ends. Referring particularly to FIG. 1, the left end of the arm 243 supports the feed push button on the keyboard (not shown) it presses the right end of arm 243 downwardly thereby tilting the left end of the arm'up and disengaging the feed rolls 40 from the stationary feed rolls 40a which are carried by the shaft 222 within the print energy and restore subassembly 100. It also closes a circuit to inhibit printing while the rolls are held open, as will be described later. Another switch 246, FIG. 3 is connected to still another keyboard'push button and serves to manually operate the paper advance and restore mechanism by pulsing the solenoid 201 to release the pawl 203. These two keyboard push buttons allow the operator to selectively open the feed rolls so that he can insert a paper form, and/or to advance the paper to a new print line. When inserting a form, he must put it all the way into the slot far enough to break the light beam from a source 247a to a photoelectric cell 247, FIG. 2, or else the output from the cell 247 will prevent resumption of printing by the printer. A sensor of this type serves to prevent faulty printing which might occur if the operator had only partially inserted the paper form.

ELECTRGNIC CONTROL CIRCUITRY The mechanical features of the printer are interconnected with electronic control features to form a cooperative combination system in which the electronic portion of the system receives the characters and the print commands from the data processing unit to which the over-all system is connected and continuously compares these received characters with the angular positions of the print character drum for coincidence. When coincidence occurs in one or more character columns of the drum, the print hammers are released in all of those columns for simultaneous printing of that particular character. It is contemplated that a whole row of characters will be printed during a single revolution of the character drum.

Referring now particularly to the block diagram of FIG. 11, the printer is assumed to be receiving characters from a data processing unit CPU which may also include a computer. The processing unit is coupled to the present electronic control circuitry by way of a cable including, for example, in the present instance 6 parallel input lines which are connected to a data latch circuit 61 and to a print command detector 71. The data latch circuit receives 6 characters at a time in parallel and converts each character for readout in serial fashion via wire 61a to a data control circuit 63. In turn, the data control circuit routes the characters on line 63a to a storage register 65. The latter register has the capability of storing 132 bits, namely 22, 6-bit characters.

The strobing of these bits and characters through the circuits 61 and 63 into the storage register is clocked by a pulse generator 64 which is preferably driven via a wire 64a coming from the data processing.

storage register, they will be followed by a print command character appearing in the 23rd character position of the message, and although there are not 23 columns on the character drum, for present purposes this print command can be thought of as occurring during a 23rd count of a counting system which will be discussed hereinafter. The 22 characters are stored in the storage register, but the print command which comprises the 23rd transferred character coming from the data processing unit CPU is not so stored.

Once the 22 print characters have been entered into the storage register, the content of this register can be then circulated in a circulating loop 66. As these bits are read from the storage register 65 they are circulated through the circulating path 66a of the loop into the data control 63 where they are returned to the line 63a and thence to the storage register. However, these sequential bits which are being circulated in this manner in the loop also enter the serial input 62 of the data latch 61 where they are latched 6 bits at a time in the bit positions of the data latch 61 in parallel fashion so that they can be momentarily read out via the parallel output lines 67 into a coincidence detector 69. In the coincidence detector they are compared with outputs appearing on the six lines 68 coming from a character counter 72. The character counter 72 is counting out the mechanical rotational positions of the character drum 20, which contains 40 rows and 22 columns of characters as was described above in detail. The character counter 72 delivers on lines 68 forty sequentially-occurring binary encoded representations of the sequentially appearing characters in the various rows of the character drum.

It will be recalled that as the character drum rotates on the shaft 21 shown in FIG. 3, it rotates a code disc 186 having two radially-spaced locations of holes, the outer holes are annularly spaced to register with the drum rows, and these holes cooperate with a photo-cell 191 to deliver index pulses indicating the arrival of each row of characters as the disc progresses. There is one radially-inner hole 188 cooperating with a photocell 192 to produce a reset pulse each time the character drum and code disc 186 have completed one revolution and are starting over again on the first row. These pulses are squared and amplified by an index generator 198 and a reset generator 199 shown in FIG. 11 but physically located on the printed circuit board 193 in FIG. 3. The system performs in such a way that each time the drum reaches its start position, i.e., the first character row, the character counter is reset by a pulse on wire 199a, and then in response to the index pulses appearing on wire 198a the character counter 72 delivers on wires 68 sequential binary readouts indicating the instantaneous positions of the character drum 20. As stated above the drum has 40 rows of characters wherein in each row the characters in all 22 columns are identical.

Thus, each readout on the wires 68 indicates which character is presently ready to be printed according to the present mechanical position of the character drum 20; and on the other hand, the readout from the data latch 61 on wires 67 indicates which character is called for at any particular moment by the data being clocked from the storage register 65 through the circulating loop 66.

It is necessaryfto understand that the readout from the storage register 65 is so much faster than the rotation of the character drum 20 that the entire contents of the storage register 65,'the sequence of 22 characters contained therein, is circulated in the loop 66 before the row position of the drum 20 can move noticeably, the circulation clock rate between 66 kilohertz. Hence the storage register reads out all 22 characters, column by column in a sequential manner, while each group of 6 bits is compared with the character represented by the output on wires 68, which is the character that can be printed according to the present position of the drum 20. The wires 67 read out the character that should be printed in the first column; then they read out the next 6 bits to represent the character which should be printed in the second column, and so on through the 22nd character. The data control circuit 63 is also used to prevent circulation of the storage register contents until the character drum has mechanically brought a particular row of characters into printing position, as distinguished from the drum being between print positions.

In order to eliminate unnecessary delays, the present system is designed so that it will not matter which row of characters is ready to be printed by the drum when the data begins circulating in the loop 66 for comparison; that is, it is not necessary for the drum to be in print-position alignment with the first character row at the time when the circulation of the stored bits commences from the register 65. Accordingly, when the index generator 198 notes that the character drum 20 is mechanically aligned in a definite print-position and ready to print a character in one of its rows, the index generator 198 delivers a pulse on the wire 198b to set the program control flip-flop and change it from a reset condition in which it inhibits circulation of the contents of the storage register 65 into a set condition in which it commences circulation of the message bits contained in the storage register. The data control circuit 63 contains data handling gates which are controlled by output on the wire 70a, depending upon its present state. When the program control flip-flop 70 is in reset condition, the data control is actuated by one signal state on wire 70a to accept new CPU data arriving via wire 61a from the data latch circuit 61, meaning input from the data processing cable 60. On the other hand, when the index generator 198 changes the program control flip-flop to set condition, the-output state on wire 70a reverses and the data control circuit 63 is inhibited from accepting further data on the input line 61a, and instead begins clocking the data from the storage register 65 through the circulating loop 66-66a. Thus, the loop begins circulating data, and this data also enters the serial input 62 of the data latch 61 and appears in parallel form on the lines 67 going to the coincidence circuit 69.

Thus, on the wires 67 there appear groups of 6-bits each representing a character being read out serially from the storage register 65, and at the same time on the lines 68 going into the coincidence detector 69 there is a binary indication of the present mechanical position of the drum 20. The coincidence detector then detects whether any of the characters being read into the lines 67 one at a time correspond with the present position of the character drum as indicated by the wires 68. If a character appearing on the wire 67 matches the present position of the drum, a coincidence signal 69a is sent to the hammer drive logic 79 to indicate that any characters which match should be printed in that position of the character drum. Again, it is pointed out that the rotation of the character drum 20 is so slow as compared with the rate at which the characters are circulated from the storage register 65 onto the lines 67 that all 22 columns can be compared for coincidence before the character drum 20 has a chance to move significantly. As a consequence, all 22 characters are read from the storage register 65 onto the lines 67 for comparison with the same drum position information appearing on the wires 68 before the position of the character drum moves from the presently registering row of characters.

The storage register message contains 22 characters corresponding with the 22 digit positions to be printed under the 22 columns of the character drum. The storage register reads these characters out sequentially starting with the character to be printed in the first column and then proceeding to the character to be printed in the second column, the third column the 22nd column. The storage register does not indicate which bits correspond with the various characters, and therefore, it is necessary to divide the flow of 132 bits from the storage register, through the recirculating loop 66 into 6-bit character groups. This is done effectively by a byte counter 73 which accepts a pulse from the data control circuit 63 for each bit being circulated therethrough at the clock rate and delivers this signal on wire 63b to step the byte counter along. The byte counter counts 6 of these pulses and then delivers output on wires 73a and 73b ,each time a 6-bit character has circulated. The output on wire 73a is used to step a column strobe counter 75 which keeps track of which column a character being circulated in the loop 66 should be placed in. The output on wire 73b after each 6-bit circulation momentarily enables the coincidence detector to deliver an output onwire 69a if that character which was just delivered is coincident with the mechanical position of the character drum 20. Thus, the column strobe counter 75- advances once for each 6-bits circulated in the storage register loop 66 as determined by the byte counter 73, whereby when the first 6-bit character is read through the circulating loop 66 the column strobe counter 75 puts out a binary indication on lines 76 indicating that this character being read from storage is the character to be printed in the first column. The output on lines 76 is decoded by the column decoder 77 which then delivers output on one wire of a 22-wire cable 77a, and since this is the first output it enables a flip-flop in the hammer drive logic which represents the first column. The hammer drive logic 79 contains 22 such flip-flops, one for each column.

When column 1 is being read from the storage register the first output wire from the column decoder 77 in the cable 77a enables the first flip-flop in the hammer drive logic 79. If the character being read from the storage register onto the lines 67 coincides with the character in the present position of the drum as indicated by the output on wires 68, a coincidence signal will appear on wire 69a and set the first column flipflop in'the hammer drive logic 79. After these 6-bits have been considered for coincidence, the byte counter 73 issues the next output on wire 73a and increments the column strobe counter 75 to the second column of print, thereby enabling the second wire in the cable 77a in turn to enable the second column flip-flop in the hammer drive logic 79. The output from the byte counter 73 on wire 73b then enables the coincidence detector to determine whether coincidence occurs between the character to be printed in the second column as appears on wires 67, and the present mechanical position of the character counter 72 as encoded on the wires 68. If coincidence again occurs, the second flip-flop in the hammer drive logic 79 is also set. In this way, all 22 characters read out from the storage resister ,65 and representing the 22 character message to be printed in the columns are sequentially compared with the same present mechanical position of the character drum 20 as indicated by the output on the wires 68 from the character counter circuit 72. All 22 characters are compared so quickly that the drum can be thought of as standing substantially still during this process, although it is in fact continuouslyrotating.

Supposing for example that the present position of the I character drum is such that an encoded letter O appears on the wires 68. As the contents of the storage register 65 are circulated, the characters which should be printed in all 22 columns are compared successively with the letter Q which appears on the wires 68. If coincidence is found in the first, third and 12th columns, for example, then the first, third and 12th flip-flops of the hammer drive logic will have been set, and the 22 wires in the cable 79a going to the printer solenoids 137 and 138 as shown in FIGS. 5 and 6 will either be enabled or not enabled depending on whether their corresponding flip-flops contained within the hammcrdrive logic 79 are set. Although each of the flip-flops will have been set, or left unset, as a result of the sampling of the characters circulated in the loop 66, nevertheless no 1 printing has yet occurred. The printing occurs according to whichof the flip-flops in the hammer logic 79 are set only when the hammer release logic 78 is sub-' sequently actuated to fire those solenoids which are associated with the set-flip-flops. Thus, the flip-flops in the hammer logic 79 are set, or else remain unset, sequentially but all of the set flip-flops are fired simultaneously only after all characters being circulated from the storage register have been compared for coincidence.

This firing of the solenoids 137 and 138 by the hammer release circuit 78 occurs in the following manner: It will be remembered that the byte counter is stepped after each 6 bits is circulated, and therefore it can be incremented as the last bit goes through the circulating loop 66 from the storage register, i.e., the l32nd bit stored therein. This bit actuates the byte counter to provide an output on wire 73a which increments the column strobe counter 75 to count its last and highest count, namely a column 23 count, even though there are only 22 columns to be printed. This column 23 count goes out on the lines 76 to the column decoder 77 which then delivers an output on wire 77b. This output performs several functions. First, it increments the strobe counter 75 back to its column 1 count. Secondly, it triggers the hammer release circuit 78 to energize via the cable 79a those printer solenoids 137 or 138 which correspond with hammer drive logic flip-flops which are set as a result of the just-completed comparison of the 22 characters contained in the storage register with the present drum position. In addition, the column 23 signal is applied to the data control circuit 63 to inhibit further circulation of the storage register contents until the character counter drum has mechanically moved to its next position and a new index generator pulse appears on wire 1980.

As soon as the character drum 20 rotates to a new character row position, an output pulse will appear on.

wire 198C to again enable the data control circuit 63 to commence circulation of the storage register contents so as to compare the stored characters with the next row of print on the drum 20. The above discussed coincidence process will start all over again, the system running through the complete contents of the storage register and comparing each of the 22 characters column by column with the new mechanical position of the character drum. As a result, some of the flip-flops in the hammer drive logic may be set by coincidences. Also, the arrival of the character drum 20 at the new index position will have provided an output from the index generator on wire 198C, and this output will have reset the hammer release circuit 78, and at the same time reset the 22 flip-flops in the hammer drive logic in preparation for the new sequence of character comparisons.

It will be recalled that it was not necessary to wait until the character drum 20 mechanically arrived at its first print character row, but instead the system merely began comparing characters at whatever position the character drum was already in. However, it is necessary to know when all 40 rows of characters have been compared with the contents of the storage register, because after 40 rows have been compared, all characters appearing on the drum will have been considered for printing by the system. Thus, when the program control flip-flop 70 is first changed from reset condition to set condition in which the storage register 65 begins circulating its contents for the first time, an output is delivered from the program control circuit 70 on the wire 70b to reset a row counter 80 to its first count. Then, after each comparison is made and the drum is arriving at a new print character position, the output of the index generator on wire 198d increments the row counter 80 to its next position. A detector 81 detects the end of the 40th count by the occurrence of its column 23 signal on wire 77b, meaning that the drum has completed one full revolution since the comparison of the contents of the storage register 65 first began, and thus all message data should have been completely printed. When this occurs, an output appears on wire 81a to reset the program control flip-flop 70 and thereby prepare the system to receive new data from the data processing unit on the cable 60. In this way, the data control is returned to a condition in which it accepts new CPU data as soon as it begins to appear in serial fashion on the wire 61a from the data latch 61. The resetting of the program control 70 also provides outputs on the wires 70d and 70c to reset the column strobe counter 75 and the column decoder 77. These circuits will not again become enabled until the program control flip-flop 70 is set once again, meaning that storage register contents are again being recirculated for comparison with the present position of the character drum, as described above. The occurrence of a print command signal on the data processing cable 60 to the print command detector 71 causes the latter to deliver an output on wire 71a enabling the flip-flop subsequently to be set by the next index pulse on wire l98b.

When 40 rows have been counted by the row counter and the 40th count has been detected by the end detector 81, meaning that a complete line of printing has been accomplished with respect to the 22 characters then contained in the storage register 65, an end" signal is delivered on wire 81b, and it is this signal which energizes the solenoid 201 appearing in FIG. 3 and disengages the pawl 203 to engage the clutch 184 and mechanically reset the hammers in the print mechanism by rotation of the shaft 171, and at the same time advance the paper in the printer by mechanical rotation of the cam 210 appearingin FIG. 9. The engaging of the clutch 184 is controlled by a control circuit 82 which includes a wire 82a which is connected to the manual advance switch 246 shown in FIG. 3 by which the printer hammers can be reset and the paper advanced to the next row manually by an operator. The control circuit 82 is inhibited from advancing by output from the program control flip-flop 70 on wire 702 when the system is actively printing so that an operator cannot accidentally manually advance the paper and thereby upset the printer performance. The photoelectric cell sensor 247, seen also in FIG. 2, inhibits setting of the program control flip-flop 70 if a paper form is manually inserted into the slot 34 in a crooked or incomplete manner.

In the absence of these inhibit signals, the printer is actuated after the completion of printing in each line to reset the hammers and advance the paper tapes 51 and 52 and any form which may have been inserted in the slot 34.

The present invention is not to be limited by the exact illustrative embodiments shown in the drawings for illustrative purposes, for obviously changes can be made within the scope of the claims.

We claim:

1. A high speed printer system for printing encoded multiple character messages from an electronic data processing unit, the printer being of the type having a character drum continuously rotated past a print position by a motor and the drum including multiple identical side by side columns of characters and the printer including means for encoding signals representing each printable character row position of the drum, the combination of:

a. a separate print hammer acceleration and impact mechanism located opposite each column of the drum;

b. an electrically released latch for each of said mechanisms and operative to 'releasably hold it in I an energy-restored position retracted away from the drum;

c. restore means operative when actuated to couple drive from the motor to retract all hammer means into latched energy-restored position;

(1. means operative each time the restore means is operative to advance paper between the hammer means and the drum; and

e. electronic control means responsive to coincidence between encoded characters in a message and encoded character drum position signals to release the latches of mechanisms in those drum positions experiencing coincidence and print those characters on the paper, and said control means being operative in response to completion of rotation of the drum past its printable character rows to actuate said restore means and said paper advance means.

2. In a printer system as set forth in claim 1, said electronic control means comprising coincidence detector means; storage means for storing and repeatedly recirculating multiple encoded message characters corresponding with the columns of the drum to be printed, means responsive to the arrival of a drum row in the print position to actuate said character recirculating means sequentially to circulate the message characters for each column in the line to be printed while comparing them with the encoded character representing that drum row employing said coincidence detector; and means operative to count the columns as they are compared and responsive to counting of the last column to be printed to inhibit recirculation of the message characters until the next drum row reaches said print position.

3. In a printer system as set forth in claim 2, said electronic control means further comprising means for counting the drum rows as they appear in the print position commencing with the row-appearing during the first recirculation of the message character stored; and means responsive to said row counting means when it has counted as many printable rows as are on the drum to actuate said restore means and said paper advance means.

4. In a printer system as set forth in claim 2, said electronic control means comprising a message data system including said storage means and including data control means for accepting new message data and entering it into said storage means, said new data including a print command; and means responsive to said print command for actuating said data control means to recirculate the stored data while excluding additional new data.

5. In a printer system as set forth in claim 1, the printer comprising a main frame supporting said motor and said rotating character drum; said means for ad vancing paper including apertured paper-feed plate means adjacent the drum; the printer further comprising a print-energy and restore assembly carried by support means secured to said frame and including said restore means, said acceleration and impact mechanisms and said latches, said mechanisms being disposed in operative relationship at said print position on the opposite side of said apertured plate means from the character drum; said print energy and restore assembly comprising as part of each of said mechanisms a hammer disposed opposite a corresponding column of the drum, guide means supporting said hammers for free reciprocation radially of the drum, a bellcrank having a first leg aligned to strike the associated hammer toward the drum and a second leg coupled to an energy spring urging the first leg toward the hammer, the bellcranks being pivoted to the assembly support means at the intersections of their legs and said latches each comprising an arm associated with a bellcrank and pivotally supported on said assembly support means and having a hook for latching one of its legs in a position to maintain its first leg retracted with respect to the hammer; and electromechanical means coupled for control by said control means and operative to displace each associated latch arm and disengage its hook from the corresponding crank leg.

6. In a printer system as set forth in claim 5, said restore means comprising bail means extending across all of the bellcranks and disposed to contact one leg of each when displaced to move the legs and restore them to latched positions in which the hooks of the arms latch one of the legs of each of the bellcranks; a restore shaft supportedby the assembly support means and carrying cam means; cam follower means coupled to displace the bail means when the cam means is rotated; and clutch means operative in response to said electronic control means to couple said restore shaft for rotation by the motor.

7. In a printer system as set forth in claim 6, said assembly support means comprising two opposed spaced side plates having bearings supporting said restore shaft which extends therethrough; a fulcrum block between said side plates and supporting said hammer guide means, the fulcrum block extending away from the drum and the hammer guide means and carrying pivots supporting said bellcranks so that the first legs of alternate cranks extend inwardly toward the hammers from opposite directions in intermeshing relationship in the vicinity of the guide; the hammers extending through the latter and lying between the first legs and the associated columns of the character drum; and the fulcrum block having other pivots supporting said latch arms respectively in alignment with their associated bellcrank legs.

8. In a printer system as set forth in claim 7, said electromechanical means comprising solenoids each having a plunger coupled to one of the latch arms to displace it from latched position; and said assembly support means including multiple solenoid deck means extending between, and supported on, opposed sides of the side plates of the print energy and restore assembly with the solenoid plungers engaging the respective latch arms which are supported on the fulcrum block.

9. In a printer system as set forth in claim 8, at least two solenoid decks supported on each of said opposed sides of the side plates, and the decks on each side supporting solenoids in interleaved mutually-staggered relationship.

10. In a printer system as set forth in claim 5, each hammer comprising a mass supported in the hammer guide parallel to all the other hammers and opposite a character column of the drum, each hammer being of such length that when the first leg of its associated bellcrank is unlatched the hammer can lie on the leg short of contact with paper which extends through the paper feed plate means; and rebound control spring means maintaining the hammer retracted from contact with the paper except when sharply struck by said first leg.

11. In a printer system as set forth in claim 10, each rebound control spring means comprising a spring wire extending through and beyond the hammer and curved toward the paper feed plate, the wire contacting and pressing against the plate when the hammer impacts the paper as a result of being struck by a leg of the associated bellcrank.

12. In a printer system as set forth in claim 11, each spring wire being bent to form a loop on each side of 

1. A high speed printer system for printing encoded multiple character messages from an electronic data processing unit, the printer being of the type having a character drum continuously rotated past a print position by a motor and the drum including multiple identical side by side columns of characters and the printer including means for encoding signals representing each printable character row position of the drum, the combination of: a. a separate print hammer acceleration and impact mechanism located opposite each column of the drum; b. an electrically released latch for each of said mechanisms and operative to releasably hold it in an energy-restored position retracted away from the drum; c. restore means operative when actuated to couple drive from the motor to retract all hammer means into latched energyrestored position; d. means operative each time the restore means is operative to advance paper between the hammer means and the drum; and e. electronic control means responsive to coincidence between encoded characters in a message and encoded character drum position signals to release the latches of mechanisms in those drum positions experiencing coincidence and print those characters on the paper, and said control means being operative in response to completion of rotation of the drum past its printable character rows to actuate said restore means and said paper advance means.
 2. In a printer system as set forth in claim 1, said electronic control means comprising coincidence detector means; storage means for storing and repeatedly recirculating multiple encoded message characters corresponding with the columns of the drum to be printed, means responsive to the arrival of a drum row in the print position to actuate said character recirculating means sequentially to circulate the message characters for each column in the line to be printed while comparing them with the encoded character representing that drum row employing said coincidence detector; and means operative to count the columns as they are compared and responsive to counting of the last column to be printed to inhibit recirculation of the message characters until the next drum row reaches said print position.
 3. In a printer system as set forth in claim 2, said electronic control means further comprising means for counting the drUm rows as they appear in the print position commencing with the row-appearing during the first recirculation of the message character stored; and means responsive to said row counting means when it has counted as many printable rows as are on the drum to actuate said restore means and said paper advance means.
 4. In a printer system as set forth in claim 2, said electronic control means comprising a message data system including said storage means and including data control means for accepting new message data and entering it into said storage means, said new data including a print command; and means responsive to said print command for actuating said data control means to recirculate the stored data while excluding additional new data.
 5. In a printer system as set forth in claim 1, the printer comprising a main frame supporting said motor and said rotating character drum; said means for advancing paper including apertured paper-feed plate means adjacent the drum; the printer further comprising a print-energy and restore assembly carried by support means secured to said frame and including said restore means, said acceleration and impact mechanisms and said latches, said mechanisms being disposed in operative relationship at said print position on the opposite side of said apertured plate means from the character drum; said print energy and restore assembly comprising as part of each of said mechanisms a hammer disposed opposite a corresponding column of the drum, guide means supporting said hammers for free reciprocation radially of the drum, a bellcrank having a first leg aligned to strike the associated hammer toward the drum and a second leg coupled to an energy spring urging the first leg toward the hammer, the bellcranks being pivoted to the assembly support means at the intersections of their legs and said latches each comprising an arm associated with a bellcrank and pivotally supported on said assembly support means and having a hook for latching one of its legs in a position to maintain its first leg retracted with respect to the hammer; and electromechanical means coupled for control by said control means and operative to displace each associated latch arm and disengage its hook from the corresponding crank leg.
 6. In a printer system as set forth in claim 5, said restore means comprising bail means extending across all of the bellcranks and disposed to contact one leg of each when displaced to move the legs and restore them to latched positions in which the hooks of the arms latch one of the legs of each of the bellcranks; a restore shaft supported by the assembly support means and carrying cam means; cam follower means coupled to displace the bail means when the cam means is rotated; and clutch means operative in response to said electronic control means to couple said restore shaft for rotation by the motor.
 7. In a printer system as set forth in claim 6, said assembly support means comprising two opposed spaced side plates having bearings supporting said restore shaft which extends therethrough; a fulcrum block between said side plates and supporting said hammer guide means, the fulcrum block extending away from the drum and the hammer guide means and carrying pivots supporting said bellcranks so that the first legs of alternate cranks extend inwardly toward the hammers from opposite directions in intermeshing relationship in the vicinity of the guide; the hammers extending through the latter and lying between the first legs and the associated columns of the character drum; and the fulcrum block having other pivots supporting said latch arms respectively in alignment with their associated bellcrank legs.
 8. In a printer system as set forth in claim 7, said electromechanical means comprising solenoids each having a plunger coupled to one of the latch arms to displace it from latched position; and said assembly support means including multiple solenoid deck means extending between, and supported on, opposed sides of the side plates of the print Energy and restore assembly with the solenoid plungers engaging the respective latch arms which are supported on the fulcrum block.
 9. In a printer system as set forth in claim 8, at least two solenoid decks supported on each of said opposed sides of the side plates, and the decks on each side supporting solenoids in interleaved mutually-staggered relationship.
 10. In a printer system as set forth in claim 5, each hammer comprising a mass supported in the hammer guide parallel to all the other hammers and opposite a character column of the drum, each hammer being of such length that when the first leg of its associated bellcrank is unlatched the hammer can lie on the leg short of contact with paper which extends through the paper feed plate means; and rebound control spring means maintaining the hammer retracted from contact with the paper except when sharply struck by said first leg.
 11. In a printer system as set forth in claim 10, each rebound control spring means comprising a spring wire extending through and beyond the hammer and curved toward the paper feed plate, the wire contacting and pressing against the plate when the hammer impacts the paper as a result of being struck by a leg of the associated bellcrank.
 12. In a printer system as set forth in claim 11, each spring wire being bent to form a loop on each side of the hammer through which it passes, and the ends of the wire beyond said loops extending toward said paper feed plate.
 13. In a printer system as set forth in claim 5, the energy springs which are each coupled at one end to a second leg of a bellcrank being fixed at their respective other ends to the assembly support means by adjustable means movable to preset the spring force on the bellcrank, and the proportions of the legs, their masses, the spring force and the mass of the hammer being selected to minimize the tendency of the hammer to impact the paper a second time after its first impact.
 14. In a printer system as set forth in claim 1, said printer including roller means operative to contact the character drum to ink the columns of characters on its surface; paper feed plate means between the drum and the hammers for guiding the paper past the surface of the drum just out of contact therewith, and the plate means having an aperture therein through which the hammers can strike the paper against the drum; and individual barrier means extending between the columns of characters on the drum and located so as to prevent the paper from undesirably contacting the characters in columns which are located adjacent to a character being intentionally impacted.
 15. In a printer system as set forth in claim 14, said barrier means comprising plural parallel wires extending across the aperture in the paper feed plate means and respectively extending between adjacent columns of characters on the drum and serving as barriers yieldably holding the paper radially outwardly from the printing surfaces of the drum.
 16. In a printer system as set forth in claim 14, said barrier means comprising plural parallel blades disposed between the adjacent columns of characters on the drum and extending closer to the paper than the printing surfaces of the characters as measured radially from the center of the drum.
 17. In a printer system as set forth in claim 14, means for supporting said ink roller means for reciprocable movement into and out of contact with said drum, and means responsive to said control means to move the roller into contact with the drum when the printer is operative.
 18. In a printer system as set forth in claim 1, plural parallel paper-feed plate means extending between the drum and the hammers for guiding the paper past the surface of the drum just out of contact therewith, and said plate means having mutually registering apertures therein through which the hammers impact the paper against the drum; and said paper advancing means including paper tape supply means for delivering paper tape between two of the plate means, And including a third plate means defining with said plate means a slot through which other paper forms can be inserted for feeding between said plate means; and feed roll means for driving the paper through the plates in unison, said printer including actuator means coupled to the restore means and disposed to rotate said feed roll means a fixed amount when the restore means is actuated by said control means.
 19. In a printer system as set forth in claim 18, said paper feed plate means including openings therethrough to receive opposed feed rolls, and said actuator being coupled simultaneously to drive both feed rolls in directions to advance the paper passing between the plate means.
 20. In a printer system as set forth in claim 19, manual means accessible exteriorly of the printer for separating the feed rolls to permit insertion of said other paper forms in said slot.
 21. In a printer system as set forth in claim 20, said electronic control means including means responsive to operation of said manual means to inhibit the other functions of the control means.
 22. In a printer system as set forth in claim 19, means for sensing full insertion of said other paper forms in the slot; and means responsive thereto to enable the control means to proceed with its other functions.
 23. A multiple digit printer, comprising: a. a motor; b. a character drum having a print column for each of said digits, the drum being coupled for rotation by the motor and having multiple rows of identical print characters; c. means for advancing paper including paper-feed plate means each having an aperture adjacent the drum; d. a print energy and restore assembly carried by support means secured to said frame and in turn supporting spring-urged print hammer acceleration and restore mechanisms including latches for holding the mechanisms in energy-restored positions, said mechanisms being disposed in operative relationship opposite the drum at the aperture in the plate means; e. said print energy and restore assembly including as part of each mechanism a hammer disposed opposite the corresponding column of the drum and guide means supporting said hammer for free reciprocation radially of the drum; f. each hammer acceleration and restore mechanism further comprising a crank having a first leg portion aligned to strike a hammer and a second leg portion coupled to an energy spring urging the first leg portion toward the hammer, the cranks being pivoted to the assembly support means; g. said latches each comprising an arm associated with a crank and pivotally supported on said assembly support means and having a hook for latching one of the leg portions in a position to maintain its first leg portion retracted with respect to the corresponding hammer; and h. selective print actuating means operative to displace each associated latch arm and disengage its hook from the corresponding crank leg portion.
 24. In a printer as set forth in claim 23, said restore means comprising bail means extending across all of the cranks and disposed to contact one leg portion of each when displaced to move the leg portions and restore the hammer accelerating mechanism to latched positions in which the hooks of the arms latch each of said one leg portions of the cranks; a restore shaft supported by the assembly support means and carrying cam means; cam follower means coupled to displace the bail means when the cam means is rotated; and clutch means operative when actuated to couple said restore shaft for rotation by the motor.
 25. In a printer as set forth in claim 24, said assembly support means comprising two opposed spaced side plates having bearings supporting said restore shaft which extends therethrough; a fulcrum block located between said side plates and supporting said hammer guide means, the fulcrum block extending away from the drum and disposed opposite to the hammer guide means and carrying pivots supporting said cranks so that the first leg portions of Alternate cranks extend inwardly toward the hammers from opposite directions in intermeshing relationship in the vicinity of the guide means, the hammers extending through the latter and lying between the first leg portions and the associated columns of the character drum; and the fulcrum block having other pivots supporting said latch arms respectively in alignment with their associated crank arms.
 26. In a printer as set forth in claim 25, said electromechanical means comprising solenoids each having a plunger coupled to one of the latch arms to displace it from latched position;and said assembly support means including multiple solenoid deck means extending between, and supported on, opposed sides of the side plates of the print energy and restore assembly with the solenoid plungers engaging the respective latch arms which are supported on the fulcrum block.
 27. In a printer as set forth in claim 26, there being at least two solenoid decks supported on each of said opposed sides of the side plates, and the decks on each side supporting solenoids in interleaved mutually-staggered relationship.
 28. In a printer as set forth in claim 23, each hammer comprising a bar supported in the hammer guide means parallel to all the other hammers and opposite a character column of the drum, each hammer being of such length that when the first leg portion of its associated crank is unlatched the hammer can lie on the leg portion short of contact with paper which extends through the paper feed plate means; and rebound control spring means maintaining the hammer retracted from contact with the paper except when sharply struck by said first leg portion.
 29. In a printer as set forth in claim 28, each rebound control spring means comprising a spring wire extending through and beyond the hammer and curved toward the paper feed plate, the wire contacting and pressing against the plate when the hammer impacts the paper as a result of being struck by a leg portion of the associated crank.
 30. In a printer as set forth in claim 29, each spring wire being bent to form a loop on each side of the hammer through which it passes, and the ends of the wire beyond said loops extending toward said paper feed plates.
 31. In a printer as set forth in claim 23, the energy springs which are each coupled at one end to a second leg portion of a crank being fixed at their respective other ends to the assembly support means by adjustable means movable to preset the spring force on the crank, and the proportions of the leg portions, their masses, the spring force and the mass of the hammer being adjusted to minimize the tendency of the hammer to impact the paper a second time after its first impact.
 32. In a printer as set forth in claim 23, said printer including roller means operative to contact the character drum to ink the columns of characters on its surface; and individual barrier means extending between the columns of characters on the drum and located so as to prevent the paper from undesirably contacting the characters in columns which are located adjacent to a character being intentionally impacted.
 33. In a printer system as set forth in claim 32, said barrier means comprising plural parallel wires extending across the aperture in the paper feed plate and respectively extending between adjacent columns of characters on the drum and serving as barriers yieldably holding the paper radially outwardly from the printing surfaces of the drum. 